diff --git a/rewrite-csharp/src/main/java/org/openrewrite/csharp/CSharpIsoVisitor.java b/rewrite-csharp/src/main/java/org/openrewrite/csharp/CSharpIsoVisitor.java
index 34369914..eee58d2f 100644
--- a/rewrite-csharp/src/main/java/org/openrewrite/csharp/CSharpIsoVisitor.java
+++ b/rewrite-csharp/src/main/java/org/openrewrite/csharp/CSharpIsoVisitor.java
@@ -15,16 +15,8 @@
  */
 package org.openrewrite.csharp;
 
-import org.jspecify.annotations.Nullable;
-import org.openrewrite.*;
-import org.openrewrite.internal.ListUtils;
-import org.openrewrite.marker.Markers;
-import org.openrewrite.tree.*;
-import org.openrewrite.java.JavaVisitor;
-import org.openrewrite.java.tree.*;
 import org.openrewrite.csharp.tree.*;
-
-import java.util.List;
+import org.openrewrite.java.tree.*;
 
 public class CSharpIsoVisitor<P> extends CSharpVisitor<P>
 {
diff --git a/rewrite-csharp/src/main/java/org/openrewrite/csharp/CSharpPrinter.java b/rewrite-csharp/src/main/java/org/openrewrite/csharp/CSharpPrinter.java
index d9115032..7041c6a2 100644
--- a/rewrite-csharp/src/main/java/org/openrewrite/csharp/CSharpPrinter.java
+++ b/rewrite-csharp/src/main/java/org/openrewrite/csharp/CSharpPrinter.java
@@ -15,13 +15,13 @@
  */
 package org.openrewrite.csharp;
 
+import org.jspecify.annotations.Nullable;
 import org.openrewrite.Cursor;
 import org.openrewrite.PrintOutputCapture;
 import org.openrewrite.Tree;
 import org.openrewrite.csharp.marker.OmitBraces;
 import org.openrewrite.csharp.marker.SingleExpressionBlock;
 import org.openrewrite.csharp.tree.*;
-import org.openrewrite.internal.lang.Nullable;
 import org.openrewrite.java.JavaPrinter;
 import org.openrewrite.java.marker.CompactConstructor;
 import org.openrewrite.java.marker.Semicolon;
@@ -714,7 +714,7 @@ private void beforeSyntax(Cs cs, CsSpace.Location loc, PrintOutputCapture<P> p)
         beforeSyntax(cs.getPrefix(), cs.getMarkers(), loc, p);
     }
 
-    private void beforeSyntax(Space prefix, Markers markers, @Nullable CsSpace.Location loc, PrintOutputCapture<P> p) {
+    private void beforeSyntax(Space prefix, Markers markers, CsSpace.@Nullable Location loc, PrintOutputCapture<P> p) {
         for (Marker marker : markers.getMarkers()) {
             p.append(p.getMarkerPrinter().beforePrefix(marker, new Cursor(getCursor(), marker), JAVA_MARKER_WRAPPER));
         }
@@ -727,7 +727,7 @@ private void beforeSyntax(Space prefix, Markers markers, @Nullable CsSpace.Locat
         }
     }
 
-    private void beforeSyntax(Space prefix, Markers markers, @Nullable Space.Location loc, PrintOutputCapture<P> p) {
+    private void beforeSyntax(Space prefix, Markers markers, Space.@Nullable Location loc, PrintOutputCapture<P> p) {
         for (Marker marker : markers.getMarkers()) {
             p.append(p.getMarkerPrinter().beforePrefix(marker, new Cursor(getCursor(), marker), JAVA_MARKER_WRAPPER));
         }
@@ -749,4 +749,4 @@ private void afterSyntax(Markers markers, PrintOutputCapture<P> p) {
             p.append(p.getMarkerPrinter().afterSyntax(marker, new Cursor(getCursor(), marker), JAVA_MARKER_WRAPPER));
         }
     }
-}
\ No newline at end of file
+}
diff --git a/rewrite-csharp/src/main/java/org/openrewrite/csharp/CSharpVisitor.java b/rewrite-csharp/src/main/java/org/openrewrite/csharp/CSharpVisitor.java
index 64bf3569..e1dbc666 100644
--- a/rewrite-csharp/src/main/java/org/openrewrite/csharp/CSharpVisitor.java
+++ b/rewrite-csharp/src/main/java/org/openrewrite/csharp/CSharpVisitor.java
@@ -17,12 +17,12 @@
 
 import org.jspecify.annotations.Nullable;
 import org.openrewrite.*;
+import org.openrewrite.csharp.tree.*;
 import org.openrewrite.internal.ListUtils;
-import org.openrewrite.marker.Markers;
-import org.openrewrite.tree.*;
 import org.openrewrite.java.JavaVisitor;
 import org.openrewrite.java.tree.*;
-import org.openrewrite.csharp.tree.*;
+import org.openrewrite.marker.Markers;
+import org.openrewrite.tree.*;
 
 import java.util.List;
 
diff --git a/rewrite-csharp/src/main/java/org/openrewrite/csharp/marker/package-info.java b/rewrite-csharp/src/main/java/org/openrewrite/csharp/marker/package-info.java
index 04db8340..14d0ea62 100644
--- a/rewrite-csharp/src/main/java/org/openrewrite/csharp/marker/package-info.java
+++ b/rewrite-csharp/src/main/java/org/openrewrite/csharp/marker/package-info.java
@@ -13,9 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-@NonNullApi
+@NullMarked
 @NonNullFields
 package org.openrewrite.csharp.marker;
 
-import org.openrewrite.internal.lang.NonNullApi;
+import org.jspecify.annotations.NullMarked;
 import org.openrewrite.internal.lang.NonNullFields;
diff --git a/rewrite-csharp/src/main/java/org/openrewrite/csharp/package-info.java b/rewrite-csharp/src/main/java/org/openrewrite/csharp/package-info.java
index 008fde1a..0f78e559 100644
--- a/rewrite-csharp/src/main/java/org/openrewrite/csharp/package-info.java
+++ b/rewrite-csharp/src/main/java/org/openrewrite/csharp/package-info.java
@@ -13,9 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-@NonNullApi
+@NullMarked
 @NonNullFields
 package org.openrewrite.csharp;
 
-import org.openrewrite.internal.lang.NonNullApi;
+import org.jspecify.annotations.NullMarked;
 import org.openrewrite.internal.lang.NonNullFields;
diff --git a/rewrite-csharp/src/main/java/org/openrewrite/csharp/tree/Cs.java b/rewrite-csharp/src/main/java/org/openrewrite/csharp/tree/Cs.java
index 88740fc7..c30f6109 100644
--- a/rewrite-csharp/src/main/java/org/openrewrite/csharp/tree/Cs.java
+++ b/rewrite-csharp/src/main/java/org/openrewrite/csharp/tree/Cs.java
@@ -18,10 +18,10 @@
 import lombok.*;
 import lombok.experimental.FieldDefaults;
 import lombok.experimental.NonFinal;
+import org.jspecify.annotations.Nullable;
 import org.openrewrite.*;
 import org.openrewrite.csharp.CSharpPrinter;
 import org.openrewrite.csharp.CSharpVisitor;
-import org.openrewrite.internal.lang.Nullable;
 import org.openrewrite.java.JavaPrinter;
 import org.openrewrite.java.internal.TypesInUse;
 import org.openrewrite.java.tree.*;
@@ -54,8 +54,7 @@ default <P> boolean isAcceptable(TreeVisitor<?, P> v, P p) {
         return v.isAdaptableTo(CSharpVisitor.class);
     }
 
-    @Nullable
-    default <P> J acceptCSharp(CSharpVisitor<P> v, P p) {
+    default <P> @Nullable J acceptCSharp(CSharpVisitor<P> v, P p) {
         return v.defaultValue(this, p);
     }
 
@@ -121,11 +120,12 @@ public SourceFile withCharset(Charset charset) {
             return withCharsetName(charset.name());
         }
 
-        @Nullable
-        public Package getPackageDeclaration() {
+        @Override
+        public @Nullable Package getPackageDeclaration() {
             return null;
         }
 
+        @Override
         public Cs.CompilationUnit withPackageDeclaration(Package packageDeclaration) {
             return this;
         }
@@ -164,15 +164,18 @@ public Cs.CompilationUnit withMembers(List<Statement> members) {
             return getPadding().withMembers(JRightPadded.withElements(this.members, members));
         }
 
+        @Override
         @Transient
         public List<Import> getImports() {
             return Collections.emptyList();
         }
 
+        @Override
         public Cs.CompilationUnit withImports(List<Import> imports) {
             return this;
         }
 
+        @Override
         @Transient
         public List<ClassDeclaration> getClasses() {
             return Collections.emptyList();
@@ -213,6 +216,7 @@ public TypesInUse getTypesInUse() {
             return cache;
         }
 
+        @Override
         public Padding getPadding() {
             Padding p;
             if (this.padding == null) {
@@ -378,8 +382,7 @@ public Padding getPadding() {
         public static class Padding {
             private final ArrayRankSpecifier t;
 
-            @Nullable
-            public JContainer<Expression> getSizes() {
+            public @Nullable JContainer<Expression> getSizes() {
                 return t.sizes;
             }
 
@@ -514,12 +517,12 @@ final class AttributeList implements Cs {
         @Nullable
         JRightPadded<Identifier> target;
 
-        @Nullable
-        public J.Identifier getTarget() {
+
+        public J.@Nullable Identifier getTarget() {
             return target == null ? null : target.getElement();
         }
 
-        public AttributeList withTarget(@Nullable J.Identifier target) {
+        public AttributeList withTarget(J.@Nullable Identifier target) {
             return getPadding().withTarget(JRightPadded.withElement(this.target, target));
         }
 
@@ -1259,8 +1262,7 @@ public Interpolation withExpression(Expression expression) {
         @Nullable
         JRightPadded<Expression> alignment;
 
-        @Nullable
-        public Expression getAlignment() {
+        public @Nullable Expression getAlignment() {
             return alignment != null ? alignment.getElement() : null;
         }
 
@@ -1271,8 +1273,7 @@ public Interpolation withAlignment(@Nullable Expression alignment) {
         @Nullable
         JRightPadded<Expression> format;
 
-        @Nullable
-        public Expression getFormat() {
+        public @Nullable Expression getFormat() {
             return format != null ? format.getElement() : null;
         }
 
@@ -1328,8 +1329,7 @@ public Interpolation withExpression(JRightPadded<Expression> expression) {
                 return t.expression == expression ? t : new Interpolation(t.id, t.prefix, t.markers, expression, t.alignment, t.format);
             }
 
-            @Nullable
-            public JRightPadded<Expression> getAlignment() {
+            public @Nullable JRightPadded<Expression> getAlignment() {
                 return t.alignment;
             }
 
@@ -1337,8 +1337,7 @@ public Interpolation withAlignment(@Nullable JRightPadded<Expression> alignment)
                 return t.alignment == alignment ? t : new Interpolation(t.id, t.prefix, t.markers, t.expression, alignment, t.format);
             }
 
-            @Nullable
-            public JRightPadded<Expression> getFormat() {
+            public @Nullable JRightPadded<Expression> getFormat() {
                 return t.format;
             }
 
@@ -1525,12 +1524,12 @@ public UsingDirective withUnsafe(boolean unsafe) {
         @Nullable
         JRightPadded<Identifier> alias;
 
-        @Nullable
-        public J.Identifier getAlias() {
+
+        public J.@Nullable Identifier getAlias() {
             return alias != null ? alias.getElement() : null;
         }
 
-        public UsingDirective withAlias(@Nullable J.Identifier alias) {
+        public UsingDirective withAlias(J.@Nullable Identifier alias) {
             return getPadding().withAlias(JRightPadded.withElement(this.alias, alias));
         }
 
@@ -1591,8 +1590,7 @@ public UsingDirective withUnsafe(JLeftPadded<Boolean> unsafe) {
                 return t.unsafe == unsafe ? t : new UsingDirective(t.id, t.prefix, t.markers, t.global, t.statik, unsafe, t.alias, t.namespaceOrType);
             }
 
-            @Nullable
-            public JRightPadded<Identifier> getAlias() {
+            public @Nullable JRightPadded<Identifier> getAlias() {
                 return t.alias;
             }
 
@@ -1657,16 +1655,17 @@ public CoordinateBuilder.Statement getCoordinates() {
             return new CoordinateBuilder.Statement(this);
         }
 
+        @Override
         public JavaType getType() {
             return typeExpression.getType();
         }
 
+        @Override
         public PropertyDeclaration withType(@Nullable JavaType type) {
             return getPadding().withType(this.typeExpression.withType(type));
         }
 
-        @Nullable
-        public NameTree getInterfaceSpecifier() {
+        public @Nullable NameTree getInterfaceSpecifier() {
             return interfaceSpecifier!= null ? interfaceSpecifier.getElement() : null;
         }
 
@@ -1674,8 +1673,7 @@ public PropertyDeclaration withInterfaceSpecifier(@Nullable NameTree interfaceSp
             return getPadding().withInterfaceSpecifier(JRightPadded.withElement(this.interfaceSpecifier, interfaceSpecifier));
         }
 
-        @Nullable
-        public Expression getInitializer() {
+        public @Nullable Expression getInitializer() {
             return initializer != null ? initializer.getElement() : null;
         }
 
@@ -1711,8 +1709,7 @@ public TypeTree getType() {
                 return pd.typeExpression;
             }
 
-            @Nullable
-            public JRightPadded<NameTree> getInterfaceSpecifier() {
+            public @Nullable JRightPadded<NameTree> getInterfaceSpecifier() {
                 return pd.interfaceSpecifier;
             }
 
@@ -1742,8 +1739,7 @@ public PropertyDeclaration withType(TypeTree type) {
                         pd.initializer);
             }
 
-            @Nullable
-            public JLeftPadded<Expression> getInitializer() {
+            public @Nullable JLeftPadded<Expression> getInitializer() {
                 return pd.initializer;
             }
 
diff --git a/rewrite-csharp/src/main/java/org/openrewrite/csharp/tree/package-info.java b/rewrite-csharp/src/main/java/org/openrewrite/csharp/tree/package-info.java
index 0d5ca5d1..97e557c1 100644
--- a/rewrite-csharp/src/main/java/org/openrewrite/csharp/tree/package-info.java
+++ b/rewrite-csharp/src/main/java/org/openrewrite/csharp/tree/package-info.java
@@ -13,9 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-@NonNullApi
+@NullMarked
 @NonNullFields
 package org.openrewrite.csharp.tree;
 
-import org.openrewrite.internal.lang.NonNullApi;
+import org.jspecify.annotations.NullMarked;
 import org.openrewrite.internal.lang.NonNullFields;